// http://www.ndesk.org/Options

//
// Options.cs
//
// Authors:
//  Jonathan Pryor <jpryor@novell.com>
//
// Copyright (C) 2008 Novell (http://www.novell.com)
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
// 
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//

// Compile With:
//   gmcs -debug+ -r:System.Core Options.cs -o:NDesk.Options.dll
//   gmcs -debug+ -d:LINQ -r:System.Core Options.cs -o:NDesk.Options.dll
//
// The LINQ version just changes the implementation of
// OptionSet.Parse(IEnumerable<string>), and confers no semantic changes.

//
// A Getopt::Long-inspired option parsing library for C#.
//
// NDesk.Options.OptionSet is built upon a key/value table, where the
// key is a option format string and the value is a delegate that is 
// invoked when the format string is matched.
//
// Option format strings:
//  Regex-like BNF Grammar: 
//    name: .+
//    type: [=:]
//    sep: ( [^{}]+ | '{' .+ '}' )?
//    aliases: ( name type sep ) ( '|' name type sep )*
// 
// Each '|'-delimited name is an alias for the associated action.  If the
// format string ends in a '=', it has a required value.  If the format
// string ends in a ':', it has an optional value.  If neither '=' or ':'
// is present, no value is supported.  `=' or `:' need only be defined on one
// alias, but if they are provided on more than one they must be consistent.
//
// Each alias portion may also end with a "key/value separator", which is used
// to split option values if the option accepts > 1 value.  If not specified,
// it defaults to '=' and ':'.  If specified, it can be any character except
// '{' and '}' OR the *string* between '{' and '}'.  If no separator should be
// used (i.e. the separate values should be distinct arguments), then "{}"
// should be used as the separator.
//
// Options are extracted either from the current option by looking for
// the option name followed by an '=' or ':', or is taken from the
// following option IFF:
//  - The current option does not contain a '=' or a ':'
//  - The current option requires a value (i.e. not a Option type of ':')
//
// The `name' used in the option format string does NOT include any leading
// option indicator, such as '-', '--', or '/'.  All three of these are
// permitted/required on any named option.
//
// Option bundling is permitted so long as:
//   - '-' is used to start the option group
//   - all of the bundled options are a single character
//   - at most one of the bundled options accepts a value, and the value
//     provided starts from the next character to the end of the string.
//
// This allows specifying '-a -b -c' as '-abc', and specifying '-D name=value'
// as '-Dname=value'.
//
// Option processing is disabled by specifying "--".  All options after "--"
// are returned by OptionSet.Parse() unchanged and unprocessed.
//
// Unprocessed options are returned from OptionSet.Parse().
//
// Examples:
//  int verbose = 0;
//  OptionSet p = new OptionSet ()
//    .Add ("v", v => ++verbose)
//    .Add ("name=|value=", v => Console.WriteLine (v));
//  p.Parse (new string[]{"-v", "--v", "/v", "-name=A", "/name", "B", "extra"});
//
// The above would parse the argument string array, and would invoke the
// lambda expression three times, setting `verbose' to 3 when complete.  
// It would also print out "A" and "B" to standard output.
// The returned array would contain the string "extra".
//
// C# 3.0 collection initializers are supported and encouraged:
//  var p = new OptionSet () {
//    { "h|?|help", v => ShowHelp () },
//  };
//
// System.ComponentModel.TypeConverter is also supported, allowing the use of
// custom data types in the callback type; TypeConverter.ConvertFromString()
// is used to convert the value option to an instance of the specified
// type:
//
//  var p = new OptionSet () {
//    { "foo=", (Foo f) => Console.WriteLine (f.ToString ()) },
//  };
//
// Random other tidbits:
//  - Boolean options (those w/o '=' or ':' in the option format string)
//    are explicitly enabled if they are followed with '+', and explicitly
//    disabled if they are followed with '-':
//      string a = null;
//      var p = new OptionSet () {
//        { "a", s => a = s },
//      };
//      p.Parse (new string[]{"-a"});   // sets v != null
//      p.Parse (new string[]{"-a+"});  // sets v != null
//      p.Parse (new string[]{"-a-"});  // sets v == null
//

using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Globalization;
using System.IO;
using System.Runtime.Serialization;
using System.Security.Permissions;
using System.Text;
using System.Text.RegularExpressions;

#if LINQ
using System.Linq;
#endif

#if TEST
using NDesk.Options;
#endif

namespace NDesk.Options {

    public class OptionValueCollection : IList, IList<string> {

        List<string> values = new List<string> ();
        OptionContext c;

        internal OptionValueCollection (OptionContext c)
        {
            this.c = c;
        }

        #region ICollection
        void ICollection.CopyTo (Array array, int index)  {(values as ICollection).CopyTo (array, index);}
        bool ICollection.IsSynchronized                   {get {return (values as ICollection).IsSynchronized;}}
        object ICollection.SyncRoot                       {get {return (values as ICollection).SyncRoot;}}
        #endregion

        #region ICollection<T>
        public void Add (string item)                       {values.Add (item);}
        public void Clear ()                                {values.Clear ();}
        public bool Contains (string item)                  {return values.Contains (item);}
        public void CopyTo (string[] array, int arrayIndex) {values.CopyTo (array, arrayIndex);}
        public bool Remove (string item)                    {return values.Remove (item);}
        public int Count                                    {get {return values.Count;}}
        public bool IsReadOnly                              {get {return false;}}
        #endregion

        #region IEnumerable
        IEnumerator IEnumerable.GetEnumerator () {return values.GetEnumerator ();}
        #endregion

        #region IEnumerable<T>
        public IEnumerator<string> GetEnumerator () {return values.GetEnumerator ();}
        #endregion

        #region IList
        int IList.Add (object value)                {return (values as IList).Add (value);}
        bool IList.Contains (object value)          {return (values as IList).Contains (value);}
        int IList.IndexOf (object value)            {return (values as IList).IndexOf (value);}
        void IList.Insert (int index, object value) {(values as IList).Insert (index, value);}
        void IList.Remove (object value)            {(values as IList).Remove (value);}
        void IList.RemoveAt (int index)             {(values as IList).RemoveAt (index);}
        bool IList.IsFixedSize                      {get {return false;}}
        object IList.this [int index]               {get {return this [index];} set {(values as IList)[index] = value;}}
        #endregion

        #region IList<T>
        public int IndexOf (string item)            {return values.IndexOf (item);}
        public void Insert (int index, string item) {values.Insert (index, item);}
        public void RemoveAt (int index)            {values.RemoveAt (index);}

        private void AssertValid (int index)
        {
            if (c.Option == null)
                throw new InvalidOperationException ("OptionContext.Option is null.");
            if (index >= c.Option.MaxValueCount)
                throw new ArgumentOutOfRangeException ("index");
            if (c.Option.OptionValueType == OptionValueType.Required &&
                    index >= values.Count)
                throw new OptionException (string.Format (
                            c.OptionSet.MessageLocalizer ("Missing required value for option '{0}'."), c.OptionName), 
                        c.OptionName);
        }

        public string this [int index] {
            get {
                AssertValid (index);
                return index >= values.Count ? null : values [index];
            }
            set {
                values [index] = value;
            }
        }
        #endregion

        public List<string> ToList ()
        {
            return new List<string> (values);
        }

        public string[] ToArray ()
        {
            return values.ToArray ();
        }

        public override string ToString ()
        {
            return string.Join (", ", values.ToArray ());
        }
    }

    public class OptionContext {
        private Option                option;
        private string                name;
        private int                   index;
        private OptionSet             set;
        private OptionValueCollection c;

        public OptionContext (OptionSet set)
        {
            this.set = set;
            this.c   = new OptionValueCollection (this);
        }

        public Option Option {
            get {return option;}
            set {option = value;}
        }

        public string OptionName { 
            get {return name;}
            set {name = value;}
        }

        public int OptionIndex {
            get {return index;}
            set {index = value;}
        }

        public OptionSet OptionSet {
            get {return set;}
        }

        public OptionValueCollection OptionValues {
            get {return c;}
        }
    }

    public enum OptionValueType {
        None, 
        Optional,
        Required,
    }

    public abstract class Option {
        string prototype, description;
        string[] names;
        OptionValueType type;
        int count;
        string[] separators;

        protected Option (string prototype, string description)
            : this (prototype, description, 1)
        {
        }

        protected Option (string prototype, string description, int maxValueCount)
        {
            if (prototype == null)
                throw new ArgumentNullException ("prototype");
            if (prototype.Length == 0)
                throw new ArgumentException ("Cannot be the empty string.", "prototype");
            if (maxValueCount < 0)
                throw new ArgumentOutOfRangeException ("maxValueCount");

            this.prototype   = prototype;
            this.names       = prototype.Split ('|');
            this.description = description;
            this.count       = maxValueCount;
            this.type        = ParsePrototype ();

            if (this.count == 0 && type != OptionValueType.None)
                throw new ArgumentException (
                        "Cannot provide maxValueCount of 0 for OptionValueType.Required or " +
                            "OptionValueType.Optional.",
                        "maxValueCount");
            if (this.type == OptionValueType.None && maxValueCount > 1)
                throw new ArgumentException (
                        string.Format ("Cannot provide maxValueCount of {0} for OptionValueType.None.", maxValueCount),
                        "maxValueCount");
            if (Array.IndexOf (names, "<>") >= 0 && 
                    ((names.Length == 1 && this.type != OptionValueType.None) ||
                     (names.Length > 1 && this.MaxValueCount > 1)))
                throw new ArgumentException (
                        "The default option handler '<>' cannot require values.",
                        "prototype");
        }

        public string           Prototype       {get {return prototype;}}
        public string           Description     {get {return description;}}
        public OptionValueType  OptionValueType {get {return type;}}
        public int              MaxValueCount   {get {return count;}}

        public string[] GetNames ()
        {
            return (string[]) names.Clone ();
        }

        public string[] GetValueSeparators ()
        {
            if (separators == null)
                return new string [0];
            return (string[]) separators.Clone ();
        }

        protected static T Parse<T> (string value, OptionContext c)
        {
            TypeConverter conv = TypeDescriptor.GetConverter (typeof (T));
            T t = default (T);
            try {
                if (value != null)
                    t = (T) conv.ConvertFromString (value);
            }
            catch (Exception e) {
                throw new OptionException (
                        string.Format (
                            c.OptionSet.MessageLocalizer ("Could not convert string `{0}' to type {1} for option `{2}'."),
                            value, typeof (T).Name, c.OptionName),
                        c.OptionName, e);
            }
            return t;
        }

        internal string[] Names           {get {return names;}}
        internal string[] ValueSeparators {get {return separators;}}

        static readonly char[] NameTerminator = new char[]{'=', ':'};

        private OptionValueType ParsePrototype ()
        {
            char type = '\0';
            List<string> seps = new List<string> ();
            for (int i = 0; i < names.Length; ++i) {
                string name = names [i];
                if (name.Length == 0)
                    throw new ArgumentException ("Empty option names are not supported.", "prototype");

                int end = name.IndexOfAny (NameTerminator);
                if (end == -1)
                    continue;
                names [i] = name.Substring (0, end);
                if (type == '\0' || type == name [end])
                    type = name [end];
                else 
                    throw new ArgumentException (
                            string.Format ("Conflicting option types: '{0}' vs. '{1}'.", type, name [end]),
                            "prototype");
                AddSeparators (name, end, seps);
            }

            if (type == '\0')
                return OptionValueType.None;

            if (count <= 1 && seps.Count != 0)
                throw new ArgumentException (
                        string.Format ("Cannot provide key/value separators for Options taking {0} value(s).", count),
                        "prototype");
            if (count > 1) {
                if (seps.Count == 0)
                    this.separators = new string[]{":", "="};
                else if (seps.Count == 1 && seps [0].Length == 0)
                    this.separators = null;
                else
                    this.separators = seps.ToArray ();
            }

            return type == '=' ? OptionValueType.Required : OptionValueType.Optional;
        }

        private static void AddSeparators (string name, int end, ICollection<string> seps)
        {
            int start = -1;
            for (int i = end+1; i < name.Length; ++i) {
                switch (name [i]) {
                    case '{':
                        if (start != -1)
                            throw new ArgumentException (
                                    string.Format ("Ill-formed name/value separator found in \"{0}\".", name),
                                    "prototype");
                        start = i+1;
                        break;
                    case '}':
                        if (start == -1)
                            throw new ArgumentException (
                                    string.Format ("Ill-formed name/value separator found in \"{0}\".", name),
                                    "prototype");
                        seps.Add (name.Substring (start, i-start));
                        start = -1;
                        break;
                    default:
                        if (start == -1)
                            seps.Add (name [i].ToString ());
                        break;
                }
            }
            if (start != -1)
                throw new ArgumentException (
                        string.Format ("Ill-formed name/value separator found in \"{0}\".", name),
                        "prototype");
        }

        public void Invoke (OptionContext c)
        {
            OnParseComplete (c);
            c.OptionName  = null;
            c.Option      = null;
            c.OptionValues.Clear ();
        }

        protected abstract void OnParseComplete (OptionContext c);

        public override string ToString ()
        {
            return Prototype;
        }
    }

    [Serializable]
    public class OptionException : Exception {
        private string option;

        public OptionException ()
        {
        }

        public OptionException (string message, string optionName)
            : base (message)
        {
            this.option = optionName;
        }

        public OptionException (string message, string optionName, Exception innerException)
            : base (message, innerException)
        {
            this.option = optionName;
        }

        protected OptionException (SerializationInfo info, StreamingContext context)
            : base (info, context)
        {
            this.option = info.GetString ("OptionName");
        }

        public string OptionName {
            get {return this.option;}
        }

        [SecurityPermission (SecurityAction.LinkDemand, SerializationFormatter = true)]
        public override void GetObjectData (SerializationInfo info, StreamingContext context)
        {
            base.GetObjectData (info, context);
            info.AddValue ("OptionName", option);
        }
    }

    public delegate void OptionAction<TKey, TValue> (TKey key, TValue value);

    public class OptionSet : KeyedCollection<string, Option>
    {
        public OptionSet ()
            : this (delegate (string f) {return f;})
        {
        }

        public OptionSet (Converter<string, string> localizer)
        {
            this.localizer = localizer;
        }

        Converter<string, string> localizer;

        public Converter<string, string> MessageLocalizer {
            get {return localizer;}
        }

        protected override string GetKeyForItem (Option item)
        {
            if (item == null)
                throw new ArgumentNullException ("option");
            if (item.Names != null && item.Names.Length > 0)
                return item.Names [0];
            // This should never happen, as it's invalid for Option to be
            // constructed w/o any names.
            throw new InvalidOperationException ("Option has no names!");
        }

        [Obsolete ("Use KeyedCollection.this[string]")]
        protected Option GetOptionForName (string option)
        {
            if (option == null)
                throw new ArgumentNullException ("option");
            try {
                return base [option];
            }
            catch (KeyNotFoundException) {
                return null;
            }
        }

        protected override void InsertItem (int index, Option item)
        {
            base.InsertItem (index, item);
            AddImpl (item);
        }

        protected override void RemoveItem (int index)
        {
            base.RemoveItem (index);
            Option p = Items [index];
            // KeyedCollection.RemoveItem() handles the 0th item
            for (int i = 1; i < p.Names.Length; ++i) {
                Dictionary.Remove (p.Names [i]);
            }
        }

        protected override void SetItem (int index, Option item)
        {
            base.SetItem (index, item);
            RemoveItem (index);
            AddImpl (item);
        }

        private void AddImpl (Option option)
        {
            if (option == null)
                throw new ArgumentNullException ("option");
            List<string> added = new List<string> (option.Names.Length);
            try {
                // KeyedCollection.InsertItem/SetItem handle the 0th name.
                for (int i = 1; i < option.Names.Length; ++i) {
                    Dictionary.Add (option.Names [i], option);
                    added.Add (option.Names [i]);
                }
            }
            catch (Exception) {
                foreach (string name in added)
                    Dictionary.Remove (name);
                throw;
            }
        }

        public new OptionSet Add (Option option)
        {
            base.Add (option);
            return this;
        }

        sealed class ActionOption : Option {
            Action<OptionValueCollection> action;

            public ActionOption (string prototype, string description, int count, Action<OptionValueCollection> action)
                : base (prototype, description, count)
            {
                if (action == null)
                    throw new ArgumentNullException ("action");
                this.action = action;
            }

            protected override void OnParseComplete (OptionContext c)
            {
                action (c.OptionValues);
            }
        }

        public OptionSet Add (string prototype, Action<string> action)
        {
            return Add (prototype, null, action);
        }

        public OptionSet Add (string prototype, string description, Action<string> action)
        {
            if (action == null)
                throw new ArgumentNullException ("action");
            Option p = new ActionOption (prototype, description, 1, 
                    delegate (OptionValueCollection v) { action (v [0]); });
            base.Add (p);
            return this;
        }

        public OptionSet Add (string prototype, OptionAction<string, string> action)
        {
            return Add (prototype, null, action);
        }

        public OptionSet Add (string prototype, string description, OptionAction<string, string> action)
        {
            if (action == null)
                throw new ArgumentNullException ("action");
            Option p = new ActionOption (prototype, description, 2, 
                    delegate (OptionValueCollection v) {action (v [0], v [1]);});
            base.Add (p);
            return this;
        }

        sealed class ActionOption<T> : Option {
            Action<T> action;

            public ActionOption (string prototype, string description, Action<T> action)
                : base (prototype, description, 1)
            {
                if (action == null)
                    throw new ArgumentNullException ("action");
                this.action = action;
            }

            protected override void OnParseComplete (OptionContext c)
            {
                action (Parse<T> (c.OptionValues [0], c));
            }
        }

        sealed class ActionOption<TKey, TValue> : Option {
            OptionAction<TKey, TValue> action;

            public ActionOption (string prototype, string description, OptionAction<TKey, TValue> action)
                : base (prototype, description, 2)
            {
                if (action == null)
                    throw new ArgumentNullException ("action");
                this.action = action;
            }

            protected override void OnParseComplete (OptionContext c)
            {
                action (
                        Parse<TKey> (c.OptionValues [0], c),
                        Parse<TValue> (c.OptionValues [1], c));
            }
        }

        public OptionSet Add<T> (string prototype, Action<T> action)
        {
            return Add (prototype, null, action);
        }

        public OptionSet Add<T> (string prototype, string description, Action<T> action)
        {
            return Add (new ActionOption<T> (prototype, description, action));
        }

        public OptionSet Add<TKey, TValue> (string prototype, OptionAction<TKey, TValue> action)
        {
            return Add (prototype, null, action);
        }

        public OptionSet Add<TKey, TValue> (string prototype, string description, OptionAction<TKey, TValue> action)
        {
            return Add (new ActionOption<TKey, TValue> (prototype, description, action));
        }

        protected virtual OptionContext CreateOptionContext ()
        {
            return new OptionContext (this);
        }

#if LINQ
        public List<string> Parse (IEnumerable<string> arguments)
        {
            bool process = true;
            OptionContext c = CreateOptionContext ();
            c.OptionIndex = -1;
            var def = GetOptionForName ("<>");
            var unprocessed = 
                from argument in arguments
                where ++c.OptionIndex >= 0 && (process || def != null)
                    ? process
                        ? argument == "--" 
                            ? (process = false)
                            : !Parse (argument, c)
                                ? def != null 
                                    ? Unprocessed (null, def, c, argument) 
                                    : true
                                : false
                        : def != null 
                            ? Unprocessed (null, def, c, argument)
                            : true
                    : true
                select argument;
            List<string> r = unprocessed.ToList ();
            if (c.Option != null)
                c.Option.Invoke (c);
            return r;
        }
#else
        public List<string> Parse (IEnumerable<string> arguments)
        {
            OptionContext c = CreateOptionContext ();
            c.OptionIndex = -1;
            bool process = true;
            List<string> unprocessed = new List<string> ();
            Option def = Contains ("<>") ? this ["<>"] : null;
            foreach (string argument in arguments) {
                ++c.OptionIndex;
                if (argument == "--") {
                    process = false;
                    continue;
                }
                if (!process) {
                    Unprocessed (unprocessed, def, c, argument);
                    continue;
                }
                if (!Parse (argument, c))
                    Unprocessed (unprocessed, def, c, argument);
            }
            if (c.Option != null)
                c.Option.Invoke (c);
            return unprocessed;
        }
#endif

        private static bool Unprocessed (ICollection<string> extra, Option def, OptionContext c, string argument)
        {
            if (def == null) {
                extra.Add (argument);
                return false;
            }
            c.OptionValues.Add (argument);
            c.Option = def;
            c.Option.Invoke (c);
            return false;
        }

        private readonly Regex ValueOption = new Regex (
            @"^(?<flag>--|-|/)(?<name>[^:=]+)((?<sep>[:=])(?<value>.*))?$");

        protected bool GetOptionParts (string argument, out string flag, out string name, out string sep, out string value)
        {
            if (argument == null)
                throw new ArgumentNullException ("argument");

            flag = name = sep = value = null;
            Match m = ValueOption.Match (argument);
            if (!m.Success) {
                return false;
            }
            flag  = m.Groups ["flag"].Value;
            name  = m.Groups ["name"].Value;
            if (m.Groups ["sep"].Success && m.Groups ["value"].Success) {
                sep   = m.Groups ["sep"].Value;
                value = m.Groups ["value"].Value;
            }
            return true;
        }

        protected virtual bool Parse (string argument, OptionContext c)
        {
            if (c.Option != null) {
                ParseValue (argument, c);
                return true;
            }

            string f, n, s, v;
            if (!GetOptionParts (argument, out f, out n, out s, out v))
                return false;

            Option p;
            if (Contains (n)) {
                p = this [n];
                c.OptionName = f + n;
                c.Option     = p;
                switch (p.OptionValueType) {
                    case OptionValueType.None:
                        c.OptionValues.Add (n);
                        c.Option.Invoke (c);
                        break;
                    case OptionValueType.Optional:
                    case OptionValueType.Required: 
                        ParseValue (v, c);
                        break;
                }
                return true;
            }
            // no match; is it a bool option?
            if (ParseBool (argument, n, c))
                return true;
            // is it a bundled option?
            if (ParseBundledValue (f, string.Concat (n + s + v), c))
                return true;

            return false;
        }

        private void ParseValue (string option, OptionContext c)
        {
            if (option != null)
                foreach (string o in c.Option.ValueSeparators != null 
                        ? option.Split (c.Option.ValueSeparators, StringSplitOptions.None)
                        : new string[]{option}) {
                    c.OptionValues.Add (o);
                }
            if (c.OptionValues.Count == c.Option.MaxValueCount || 
                    c.Option.OptionValueType == OptionValueType.Optional)
                c.Option.Invoke (c);
            else if (c.OptionValues.Count > c.Option.MaxValueCount) {
                throw new OptionException (localizer (string.Format (
                                "Error: Found {0} option values when expecting {1}.", 
                                c.OptionValues.Count, c.Option.MaxValueCount)),
                        c.OptionName);
            }
        }

        private bool ParseBool (string option, string n, OptionContext c)
        {
            Option p;
            string rn;
            if (n.Length >= 1 && (n [n.Length-1] == '+' || n [n.Length-1] == '-') &&
                    Contains ((rn = n.Substring (0, n.Length-1)))) {
                p = this [rn];
                string v = n [n.Length-1] == '+' ? option : null;
                c.OptionName  = option;
                c.Option      = p;
                c.OptionValues.Add (v);
                p.Invoke (c);
                return true;
            }
            return false;
        }

        private bool ParseBundledValue (string f, string n, OptionContext c)
        {
            if (f != "-")
                return false;
            for (int i = 0; i < n.Length; ++i) {
                Option p;
                string opt = f + n [i].ToString ();
                string rn = n [i].ToString ();
                if (!Contains (rn)) {
                    if (i == 0)
                        return false;
                    throw new OptionException (string.Format (localizer (
                                    "Cannot bundle unregistered option '{0}'."), opt), opt);
                }
                p = this [rn];
                switch (p.OptionValueType) {
                    case OptionValueType.None:
                        Invoke (c, opt, n, p);
                        break;
                    case OptionValueType.Optional:
                    case OptionValueType.Required: {
                        string v     = n.Substring (i+1);
                        c.Option     = p;
                        c.OptionName = opt;
                        ParseValue (v.Length != 0 ? v : null, c);
                        return true;
                    }
                    default:
                        throw new InvalidOperationException ("Unknown OptionValueType: " + p.OptionValueType);
                }
            }
            return true;
        }

        private static void Invoke (OptionContext c, string name, string value, Option option)
        {
            c.OptionName  = name;
            c.Option      = option;
            c.OptionValues.Add (value);
            option.Invoke (c);
        }

        private const int OptionWidth = 29;

        public void WriteOptionDescriptions (TextWriter o)
        {
            foreach (Option p in this) {
                int written = 0;
                if (!WriteOptionPrototype (o, p, ref written))
                    continue;

                if (written < OptionWidth)
                    o.Write (new string (' ', OptionWidth - written));
                else {
                    o.WriteLine ();
                    o.Write (new string (' ', OptionWidth));
                }

                List<string> lines = GetLines (localizer (GetDescription (p.Description)));
                o.WriteLine (lines [0]);
                string prefix = new string (' ', OptionWidth+2);
                for (int i = 1; i < lines.Count; ++i) {
                    o.Write (prefix);
                    o.WriteLine (lines [i]);
                }
            }
        }

        bool WriteOptionPrototype (TextWriter o, Option p, ref int written)
        {
            string[] names = p.Names;

            int i = GetNextOptionIndex (names, 0);
            if (i == names.Length)
                return false;

            if (names [i].Length == 1) {
                Write (o, ref written, "  -");
                Write (o, ref written, names [0]);
            }
            else {
                Write (o, ref written, "      --");
                Write (o, ref written, names [0]);
            }

            for ( i = GetNextOptionIndex (names, i+1); 
                    i < names.Length; i = GetNextOptionIndex (names, i+1)) {
                Write (o, ref written, ", ");
                Write (o, ref written, names [i].Length == 1 ? "-" : "--");
                Write (o, ref written, names [i]);
            }

            if (p.OptionValueType == OptionValueType.Optional ||
                    p.OptionValueType == OptionValueType.Required) {
                if (p.OptionValueType == OptionValueType.Optional) {
                    Write (o, ref written, localizer ("["));
                }
                Write (o, ref written, localizer ("=" + GetArgumentName (0, p.MaxValueCount, p.Description)));
                string sep = p.ValueSeparators != null && p.ValueSeparators.Length > 0 
                    ? p.ValueSeparators [0]
                    : " ";
                for (int c = 1; c < p.MaxValueCount; ++c) {
                    Write (o, ref written, localizer (sep + GetArgumentName (c, p.MaxValueCount, p.Description)));
                }
                if (p.OptionValueType == OptionValueType.Optional) {
                    Write (o, ref written, localizer ("]"));
                }
            }
            return true;
        }

        static int GetNextOptionIndex (string[] names, int i)
        {
            while (i < names.Length && names [i] == "<>") {
                ++i;
            }
            return i;
        }

        static void Write (TextWriter o, ref int n, string s)
        {
            n += s.Length;
            o.Write (s);
        }

        private static string GetArgumentName (int index, int maxIndex, string description)
        {
            if (description == null)
                return maxIndex == 1 ? "VALUE" : "VALUE" + (index + 1);
            string[] nameStart;
            if (maxIndex == 1)
                nameStart = new string[]{"{0:", "{"};
            else
                nameStart = new string[]{"{" + index + ":"};
            for (int i = 0; i < nameStart.Length; ++i) {
                int start, j = 0;
                do {
                    start = description.IndexOf (nameStart [i], j);
                } while (start >= 0 && j != 0 ? description [j++ - 1] == '{' : false);
                if (start == -1)
                    continue;
                int end = description.IndexOf ("}", start);
                if (end == -1)
                    continue;
                return description.Substring (start + nameStart [i].Length, end - start - nameStart [i].Length);
            }
            return maxIndex == 1 ? "VALUE" : "VALUE" + (index + 1);
        }

        private static string GetDescription (string description)
        {
            if (description == null)
                return string.Empty;
            StringBuilder sb = new StringBuilder (description.Length);
            int start = -1;
            for (int i = 0; i < description.Length; ++i) {
                switch (description [i]) {
                    case '{':
                        if (i == start) {
                            sb.Append ('{');
                            start = -1;
                        }
                        else if (start < 0)
                            start = i + 1;
                        break;
                    case '}':
                        if (start < 0) {
                            if ((i+1) == description.Length || description [i+1] != '}')
                                throw new InvalidOperationException ("Invalid option description: " + description);
                            ++i;
                            sb.Append ("}");
                        }
                        else {
                            sb.Append (description.Substring (start, i - start));
                            start = -1;
                        }
                        break;
                    case ':':
                        if (start < 0)
                            goto default;
                        start = i + 1;
                        break;
                    default:
                        if (start < 0)
                            sb.Append (description [i]);
                        break;
                }
            }
            return sb.ToString ();
        }

        private static List<string> GetLines (string description)
        {
            List<string> lines = new List<string> ();
            if (string.IsNullOrEmpty (description)) {
                lines.Add (string.Empty);
                return lines;
            }
            int length = 80 - OptionWidth - 2;
            int start = 0, end;
            do {
                end = GetLineEnd (start, length, description);
                bool cont = false;
                if (end < description.Length) {
                    char c = description [end];
                    if (c == '-' || (char.IsWhiteSpace (c) && c != '\n'))
                        ++end;
                    else if (c != '\n') {
                        cont = true;
                        --end;
                    }
                }
                lines.Add (description.Substring (start, end - start));
                if (cont) {
                    lines [lines.Count-1] += "-";
                }
                start = end;
                if (start < description.Length && description [start] == '\n')
                    ++start;
            } while (end < description.Length);
            return lines;
        }

        private static int GetLineEnd (int start, int length, string description)
        {
            int end = Math.Min (start + length, description.Length);
            int sep = -1;
            for (int i = start; i < end; ++i) {
                switch (description [i]) {
                    case ' ':
                    case '\t':
                    case '\v':
                    case '-':
                    case ',':
                    case '.':
                    case ';':
                        sep = i;
                        break;
                    case '\n':
                        return i;
                }
            }
            if (sep == -1 || end == description.Length)
                return end;
            return sep;
        }
    }
}

